The Photosensitized Dimerization of Molecules Containing Conjugated Double and Triple Bonds

Both thermal and photosensitized dimerization of methacrylonitrile in solution lead to a mixture of three dimers, the ratio of which merely depends on the reaction conditions. A common 1,4‐biradical intermediate is assumed to be the precursor of all three dimers. The mechanism of the photosensitized dimerization of methacrylonitrile was studied by measuring quantum yields and by using sensitizers of different triplet energies. On the other hand, in the thermal and photosensitized dimerization of isopropenylacetylene at least two different biradical intermediates have to be postulated in order to explain the formation of the observed products.